Sealed Frames For Preservation - For Preservation

Sealed Frames
For Preservation
A Supplement to
Picture Framing Magazine
April 2002
by Hugh Phibbs
SEALED
Frames for Preservation
Introduction
The terms "preservation" and
"framing" fit together uneasily. Works
on paper, fabric, or animal skin can
best be preserved if they are stored in
by Hugh Phibbs
polyamide, or polyester. Each of these
polymers has a melting point that is
higher than that of polyethylene and
allows for heat bonding of the inner
layer, while the outer layer remains
in an environment that has stable,
non-extreme condition and it must be
protected from water that might come
from an accident with a sprinkler
system, it can be sealed in a package
a dark, stable, safe environment. intact. glazed with acrylic sheet. Glass is
Framing is a form of display and as These films can be used to isolate needed for packages that will be
long as a frame is on view, its contents wooden elements, such as fillets or exposed to fluctuating or extreme
are exposed to light. Even with the frame rabbet edges, from the contents exterior condition and when static on
ultraviolet wavelengths filtered out, of the frame. If a sheet of one of these the glazing might pose a problem.
light will cause change in these mate- films is substituted for the dust cover The last decade has seen the devel-
rials. The decision to house something paper on the back of the frame, it can opment of packages sealed with heat
in a frame must be made with the isolate the contents of the frame from and either double-sided pressure-
knowledge of the effects that long dampness that may come from the sensitive tape or electrical-grade hot
term exposure to light will have on wall behind it without the creation of melt glue. Designs have evolved to
that item. a highly sealed package in the frame. accommodate both matted works and
The frame can provide invaluable Finally, they can also be used to create works that have the form of paintings
protection for its contents against packages that seal in the proper condi- on either stretched canvas or on
mishandling and physical accidents. If tions to which the matting and the panel. These developments and tech-
it is properly designed, it can shield its framed item have been acclimated and niques have been described as they
contents from physical and chemical can maintain those conditions indefi- have come into service and are gath-
pollution and from the effects of fluc- nitely, if vapor-barrier glazing is used. ered, here, into the first complete
tuating and extremes of relative Glass is crystalline enough to func- overview of this topic.
humidity. These last features have tion as a vapor-barrier, and if it is
become more widely available in the used in a laminate, with two lites of Some Cautions with Relative
last decade as designs for highly sealed glass bonded together or with glass Humidty
packages have been developed to outside of acrylic sheet, it will provide Fears about unintentionally creating
enhance the role of well-designed both safety and a barrier to the overly damp conditions in the mat
frames as useful preservation tools. passage of moisture. Acrylic sheet has package make many framers shy away
The most important element in less vapor-barrier potential and it will from truly sealing frames. The vision
highly sealed framing is laminated warp if its sides are exposed to of mold growing inside a frame or
sealing film. This material has been differing levels of relative humidity. foxing occurring on the matting can
used for decades in military applica- This means that the break-resistant easily give one pause, and framers
tions and food and medical pack- safety it offers must be weighed should be applauded for their caution.
aging. Many types comprise an inner, against the possibility that sealed The questions surrounding relative
bonding layer of polyethylene, an packages glazed with it can loose their humidity (RH) are not, however, as
aluminum layer that serves as a vapor initial conditioning, eventually. If arcane as they might appear.
barrier, a second layer of polyethylene such a package is kept in a climate Extremely dry conditions are a
that bonds the aluminum to the with conditions drier than those in grave threat to wood and wood lami-
outer, puncture-resistant layer of the package, it will warp in toward nates, ivory, hides, horn, bone, many
plastic, and the outer layer. The outer the art. paint films, and glue layers. As such
layer may be made of polypropylene, When the framed work will be kept materials become desiccated, they can
April Preservation Supplement 2002_ PFM 3
crack and change shape; paper Thymol is the most common of these. the case of clients who bring in works
becomes brittle and more fragile. However, many fungicides tend to with mold from homes with well-
When can such conditions be discolor the paper to which they have controlled climates. Interior walls
expected? Land areas which are far been applied when exposed to light which connect with attic or crawl
from sources of airborne water have for a period of time. These fungicidal spaces and are open to outside air may
dry climates. The high plains of our materials are also highly volatile and present the same problem.
Rocky Mountain region experiences cannot be expected to protect treated Sealing the mat/glass package can
conditions of relative humidity materials from future infestations. defend against both very wet or dry
which may hover around 20% Ultimately, the simplest answer to conditions, but the framer must be
annually. Collectors in that region the problem of mold and mildew is to familiar with proper sealing tech-
would do well to focus on items avoid damp conditions. To accom- niques, as well as with management of
made of metal and to avoid leather, plish this, one must appreciate the condition in the shop. This way, the
wood, and the like. varied sources of high relative contents will be properly conditioned
When a residence is heated, air humidity. before the seal is made.
from the furnace will be desiccated. Those who live very close to the Keeping the relative humidity in a
Even an effective humidification ocean and other salt water bodies are frame shop within a safe range may be
unit will be hard pressed to keep the affected not only by the moisture, but easier than it first sounds. If one
relative humidity in the home at also from salt which is borne inland as considers how often items in the shop
50% at 70°F. Air which is that an atmospheric aerosol. Metals will be have grown mold, or how many have
humid may condense on the inside very difficult to maintain here. Other shown signs of new foxing, one will
of the windows of the home or its items should be given as much protec- have an idea of how often the relative
exterior walls. tion as possible. humidity has been dangerously high
An item in an unsealed frame in a In the U.S., most residents will be for a long enough period to cause
home will likely go through a dry affected by damp stretches of weather damage. Even if the shop is briefly
phase during the winter. Since most during at least part of the year. Air exposed to dangerously high condi-
framed materials are not overly sensi- conditioning is a first line of defense. tions (due to power failure in the
tive to dry conditions, this is usually Room dehumidifiers are often summer, or flooding), the endangered
not a problem. designed with a bucket to collect materials can be moved to a safer
A dry phase will probably not occur condensation. This would be imprac- place or sequestered in vapor barrier
in areas which do not have significant tical with an air conditioner, since it materials before they become damp.
amounts of heated air in the winter. draws so much water from the air that Looking at the other side of the
In Hawaii or southern Florida, for emptying its bucket would be humidity issue, materials which will
instance, a frame may be in relatively constant. Most homes with central air suffer from exposure to low relative
damp conditions year round. Here, conditioning will have conditions humidity—wooden panels and inlay,
the framed item is in constant peril of drier than mold requires. ivory, oil paintings with hide glue
foxing or mold growth. When relative Even homes with window units are grounds, and thick layers of gum in
humidity exceeds 65% at 70°F, mold usually not very moist for long watercolor and gouache—are not
may begin to grow. periods, since clothing and fabric on frequently brought in for framing.
The germinal parts, commonly the back sides furniture would begin When such an item is brought in
called spores, are actually conidia. to mold if they were. Mold requires during a dry period, it can be kept in
They are airborne and can be found still air to grow, so air movement will a vapor barrier bag with a conditioned
on most surfaces which have been discourage growth on open surfaces. blotter or board until it is framed.
exposed to the air. As the moisture Trapped air may be a factor in the To understand and control relative
available to them increases, they can growth of mold, but architectural humidity one must first be able to
begin to send rootlike filaments into moisture is probably a greater cause. watch it change. The least expensive
organic materials such as paper, wood, Exterior building walls without a monitor for relative humidity is a
or hide. They extract nutrients and vapor barrier layer will allow moisture cobalt salt card. A pack of five of
produce more fruiting bodies which through and into the room. This is these cards can be found in most
can be seen on the surface of the true of older construction and of preservation supply catalogues for less
infested material. If relative humidity masonry walls. If moisture comes than $10. If these cards are fixed to a
is lowered, their destructive growth is through the wall into the back of the wall in each room of the shop and to
arrested but potential for future frame, it may become trapped, the inside of storage units (such as
growth remains. making the relative humidity in the map drawers), the staff can begin to
In the past, antifungal materials frame higher than that of the room. get a sense of how the conditions
were used to address this problem. This may be what is happening in fluctuate in each area over a year. An
4 PFM _ April Preservation Supplement 2002
electronic hygrometer will also be system, attention should be paid to can keep a material supple by holding
useful in tracking the conditions of the amount of moisture which they its molecular structure apart so link-
the air in the shop and will provide a contain. If a paper-based item has ages, which would create more
check on the cards. come in from an automobile on a rigidity, cannot form. This sort of
Tracking the changes shown by the damp day, it can be placed in a clear material may migrate out of the
cards is likely to reveal that the shop polyethylene bag with a cobalt salt substance to which it was added.
will be on the dry side of 50% far card and watched for an hour or so. This could be especially troublesome
more often than it is on the damp Anything to which hinges have been if it migrated out into a closed
side, unless it is located in a basement. attached should also be kept out of environment.
Each building has areas of greater and the drawers until it is thoroughly dry. One question to ask in designing a
lesser fluctuation in relative humidity. The same is true for any board which package which will house something
Exterior walls are an obvious source comes into the shop, especially if it valuable and especially a package
for concern. has been delivered during a time which is to be sealed, is: Do any of
Furthermore, few buildings are when the weather is damp. the materials to be used have an odor?
designed with vapor barriers in their The human nose may not be as acute
walls. Plastic sheeting can slow the Basic Frame Sealing as that of other mammals, but it can
passage of water vapor, but an addi- There are a number of factors detect a vast array of off-gassing mole-
tional layer of metal foil is required which must be considered in the cules. Some things like hinging paste
for complete vapor barrier protection. context of frame sealing. What is may have a benign odor, but a tape
Since there is little likelihood that any being sealed in and what is being which smells of vinegar is probably
outside walls in the shop can be sealed out? How long can the seal be emitting acetic acid. If the materials
expected to have complete vapor expected to last? How effective will to be used inside the package have
barriers in them, critical functions the seal be under different conditions? been determined to be stable and
such as art and board storage should How difficult and expensive will it be inert, the next question involves the
not be adjacent to these walls. to establish various levels of sealing of nature of the seal and what it will
Interior walls must also be exam- the package? How much benefit can exclude.
ined to see whether they communi- be expected from a sealed package? Different materials can be used to
cate with attic or crawl spaces which The materials which are to be seal out particulate and gaseous pollu-
have untreated air in them. Warm, sealed in a package with a work of art tion, humidity, and light. Nothing
damp air in the summer can move on paper should be as well known— can give long term insulation from
into such walls and humidify them. In and, therefore, as simple—as possible. changes in temperature, so the effect
the winter, cold air moving through The fewer the variables that are of these changes on the materials and
such walls can lower their temperature included, the fewer chances there are on the design of the package must be
and make them condensation sites if for an unanticipated problem. If the considered. No package containing
the room air has been humidified. components have been proven over any materials which are conditioned
In light of these considerations, the long periods of time to have no to higher than accepted relative
simplest strategy is a concentration on adverse effect on delicate art which humidity conditions can be safely
local control of humidity. Concen- has been stored in proximity to them, sealed. Indeed, since packages which
trating on the areas where the matting they should work well in the future. contain glazing will transmit water
materials and works to be framed are Boards and hinging materials made of vapor through their glazing, having
stored allows relatively small effort to pure cellulose will be chemically the materials to be sealed slightly on
produce significant results. The similar to the paper on which the art the dry side will permit a greater
storage drawers can be shielded with has been done, as will vegetable starch margin for safety. The accepted
vapor barrier film (an hinging paste which, like paper, is a conditions referred to here are
aluminum/plastic laminate) which polysaccharide. Synthetic glues have a 50% RH at 70°F or roughly 20°C.
encloses the bottom, back, top, and less proven track record than animal Most art on paper will do well in
sides. They will be open to the air in and vegetable glues and pastes, but somewhat dryer conditions than
the room, but this can be tracked. It the best of the synthetics certainly these, but extreme drying will cause
is also possible to make large pouches seem to be stable and relatively inert. the paper to become brittle and will
which will fit into the drawers them- The inclusion of plasticizers and cause paint films and emulsions to
selves. The pouches can be fashioned tackifiers in pressure-sensitive adhe- crack. If a package with damp compo-
by ironing the laminate to itself. If sives raises more questions. These nents is sealed, the relative humidity
separate side pieces are used, it will additives are often not chemically can rise as it cools and cross the
accommodate larger loads. linked to the material which they are threshold at which fungal growth can
When materials are added to the modifying. A plasticizer, for instance, occur (namely, 65 to 70%). A damp
6 PFM _ April Preservation Supplement 2002
package may also experience conden- laminated glass. A double-sided pres- Environments in which brief,
sation if it is suddenly illuminated sure-sensitive tape is used to bond the unavoidable periods of high relative
strongly and the paper products and matte, polyethylene side of the film to humidity occur can be protected
air within warm up more rapidly than the front and edges of the glazing. If a against by such packaging. This
the glazing. window mat is used the film can be package will eventually absorb
Excess humidity must never be further fused to the tape with heat dangerous amounts of moisture if left
sealed in. The only true barrier to provided by a household or tacking in constantly high conditions and can
humidity is a metal film. Most coat- iron set on medium high. The wrin- not be used unless there will be an
ings and plastics sheets and boards kling of the film will reveal the estab- alteration of high and low relative
will permit the passage of water and lishment of the bond. If a window humidity. This highly sealed package
other vapors. The exact rate of this mat is not used and the art comes is only one among many options
transmission is too complicated a within an inch or less of the edge, the which can be employed to shelter
question to be factored in to the laminate should be reversed so that its framed art work from environmental
design of a framing package, but it shiny, nylon side will be inside, as this harm.
can be said that the thicker the mate- will give a much superior cold bond Pressure sensitive tapes are
rial, the slower and less efficient its to the acrylic tape. In both cases, the frequently used by framers to seal the
transmission. excess film should be trimmed off edges of the glazing in a frame. If the
While much of the gaseous pollu- using the same technique employed tape is applied between the edge of
tion which comes from our atmos- for trimming the backing paper on glazing and the rabbet, it may serve to
phere will be sealed out by a plastic picture frames. keep dust from coming under the lip
barrier, a sacrificial
metal scavenger (such Figure 1
as active copper) or
molecular sieve is
needed to give such a
layer the kind of effi-
cacy which
approaches that of a
metal foil. Since the
metal foil will stop
the passage of water
vapor, it can not be
safely used in framing
unless the materials and environment This package will have relatively of the frame for a time. There is,
involved in constructing the frame high resistance to the influx of water however, not much dust which will
can be guaranteed to be conditioned vapor. That resistance can be multi- enter through this route if the frame
in the proper range. If this can not be plied by the inclusion of properly has a smooth, flat lip. The grip of
provided, the sealing out of pollution conditioned silica gel impregnated the tape on the frame will eventually
may be effected through the use of paper. This material has many times give up.
the plastic barrier and may be the capacity of paper to absorb and A more common practice is the
enhanced by the addition of the scav- release moisture and it can buffer the application of tape to the edges of the
enging material while water vapor is contents of such a sealed package glazing in the front of the package
allowed to enter and leave at a against transmission of water vapor and around to the edges of the
reduced rate. though the glazing for much longer backing board in the rear. This leaves
Briefly stated, the technique of basic periods. A strip of cobalt salt the adhesive coated side of the tape
frame sealing comprises surrounding humidity indicator card can be placed pointed in toward the interior of the
the properly conditioned matting under the edge of the glazing, and on package and the art it contains. As the
materials and the art which they top of the edge of the window mat, so tape ages its volitiles can infuse into
house with a solid sheet of that it will hide from all but the most the package with potentially undesir-
aluminum/plastic laminate (such as inquisitive eyes under the lip of the able results. This problem can be
MarvelSeal 360 or 470, or Mitsubishi frame [Figure 1]. This will permit overcome by facing the inside of the
PE/AL/PE/PET). The sheet of lami- the owner, who has been briefed as tape with an impervious barrier.
nate is pulled around the sides of the to what to look for, to monitor the One simple candidate is the
mat package and secured to the side condition inside the package plastic/aluminum sheet. This material
and the front of a sheet of acrylic or periodically. comes in long rolls which can be cut
8 PFM _ April Preservation Supplement 2002
into small segments on a power miter for the normal range of conditions allow gases to enter and exit through
box to produce small rolls of whatever which a frame can be expected to the acrylic. This type of package can
thickness is needed to face the part of encounter. work well in situations in which the
the pressure-sensitive tape which will A weak point in that design is its climate may fluctuate but will not
extend around the side of the mat use of pressure-sensitive adhesive. This maintain high or low RH conditions
[Figure 2]. This can be applied by material can fail if the pressure inside over time. If a package is to be placed
running the tape along the face of the the package exceeds the pressure in an environment which has high or
glass and leaving it extended from that outside of it. That can be the case if low relative humidity consistently over
edge while the laminate is applied to the package experiences a change in long periods of time, glass should be
the extended portion [Figure 3]. If the altitude. The seams of the package at substituted for the acrylic glazing.
polyethylene side is applied to the When a package is made using
adhesive on the tape, it will be easier Figure 2 acrylic sheet, the edges of the produc-
to reposition if it goes astray and the tion paper can be peeled back along
inert nylon side will face in toward the the edges and folded over onto them-
art. Other materials such as rolled selves. This will expose the edge of the
polyester sheet can be used to perform sheet while it protects the rest and will
this role but their barrier potential is lift the straightedge up off the surface
not as great. so that it does not become stuck in
Any pressure-sensitive tape which is the hot glue. The glue should be
used to seal a frame will loose its hold extruded onto the edges with the same
as it ages. The more its adhesive is technique used for caulking. The glue
protected from oxygen and oxidizing is pushed out in front
gases, the longer it will maintain its of the nozzle. After the
bond strength. This is one the glue has been extruded
purposes in sheltering the adhesive along one edge, the
inside the laminate in the highly Figure 3 sheet should be turned
sealed package described here. The so that it can next be
material to which the tape is applied its corners are also a weak point. set on the opposite edge. When both
must also be considered in assessing Where one layer of tape crosses of those lines of glue are cool, it can
the longevity of the tape bond. Tape another, small gaps will occur which be applied to the remaining two sides.
stuck to metal will be sheltered by cannot be flattened by the application Using this pattern reduces the possi-
that metal and tape suck to glazing of heat. This can be demonstrated by bility that the straight edge will
and plastic boards will also be some- placing such a package under water become fouled in still warm glue.
what sheltered by those materials. and applying pressure. Small bubbles If glass is required for a sealed
Aging gases can still permeate the issuing from these corner sites are package, it should be laminated or
carrier of the tape itself or penetrate evidence of this problem. used in combination with acrylic
from its edges, but this will be signifi- More durable packages can be made sheet. If a package were made with
cantly less than the amount which can if an electrical-grade hot melt adhesive unlaminated glass and it simply
be expected to come through a paper (such as 3M 3797 or 3748) is substi- cracked, there might be an extended
board or wood. tuted for the pressure-sensitive tape. interval in which the inside of the
Tapes with poor quality rubber The best of these adhesives are made package slowly changed its condi-
family adhesives can be expected to of polyethylene and or polypropylene. tioning. This is because the sides of a
oxidize and release their hold sooner Those made of polyvinyl acetate or crack in a lite of glass are so close
than acrylic family adhesives. Tapes ethylene vinyl acetate can be expected together that water vapor can not
are not the most physically rugged to give off acetic acid in time. The move through rapidly. If the glass
method of creating a seal, but the use better hot melt adhesives need a high broke and pieces dislodged, the
of gasketing and pressure sealing temperature, industrial quality gun for package could loose its conditioning
requires so much support structure application. This higher temperature quite rapidly.
and expense that it is not yet practical allows the glue to bond more success- Before the glue is applied to the
for use in commercial framing. fully to other polymers. edges of the glass, they should be
Before the glue is applied, the edges washed with alcohol to remove any
Advanced Frame Sealing of the glazing sheet must be dulled so greasy residue which might disable the
This basic method just explained that they will not cut through the bond. The bond which the hot melt
will perform well as a barrier to rela- laminate. If a package is to be made makes to the surface of glass is less
tive humidity and can be quite useful using acrylic sheet as its glazing, it will adhesive than that which it makes to
April Preservation Supplement 2002_ PFM 9
the surface of acrylic sheet. The When either type of work is being When the temperature in the package
temperature of the hot melt is high sealed, its condition and the condition rises, the air will be able to hold more
enough that it can bond readily with of the materials which will be sealed moisture, which the cellulose will
the acrylic, but this is not the case with it must be established as being in contribute to it. The relatively high
with glass. Lines of glue must be an appropriate range. This can be proportion of cellulose to air in this
applied to the edges of the lite of glass done with nothing more expensive type of package means that there
on both sides. This permits the lami- than a cobalt salt indicator card which should never be a problem if the mate-
nate, which will form the skin of the has been enclosed in a plastic bag rials are conditioned.
package, to be secured to both sides of When a painting is enclosed, there
Figure 4
the glass and then bonded to itself just will be more air in the package. The
outside the edge of the glass, creating a spacer which holds the painting away
more durable seal [Figure 4]. from the surface of the glazing will
The heat needed for the creation of create an air space, as will the hollow
these packages will be the same as was in back of the painting between the
required when double-sided tape was sides of the stretcher. The wood of the
Figure 5
employed: roughly three quarters of stretcher will form a highly efficient
the maximum heat which most reservoir to buffer conditions inside of
tacking irons will provide. To find the the package, and stretched canvases are
proper setting, one should practice less sensitive to fluctuations in RH
bonding the laminate to itself and to than works of art on paper.
cooled extruded hot melt. When the A painting on a wooden panel of
silver surface of the laminate film has the antique variety, however, can be
acquired a wrinkled appearance, it has Figure 6 quite sensitive as it expands across its
reached bonding temperature. If it grain. These are not frequently found
maintains a smooth surface, the bond in the work stream of frame shops,
may be suspect. The film should and if one were brought in with the
always be bonded to other materials or request that it be sealed, a conservator
to itself using the matte, polyethylene should be consulted. Pressed and lami-
side as the nated wood panels are not so reactive,
bonding surface. and can therefore be regarded as being
Figure 7
The shiny, nylon more similar to stretched canvases.
side will be the If more condition buffering is
side which faces needed, paper impregnated with silica
the outside of the gel can be obtained from conservation
package. suppliers. This material is a very effi-
Since the adhesive used here is more along with the material in question for cient reservoir for water vapor. It
difficult to apply and bond in a a few hours. Everything which will be works because it has an extensive
controlled manner than was the case inside the package must be condi- surface area to which these polar mole-
with double-sided tape, the frame may tioned to 50% RH at 70°F. cules will loosely bond. Since the silica
need to be chosen or modified accord- If conditions with more humidity get is many times more effective than
ingly. The lip or rabbet width of the are permitted, there may be circum- paper as an RH reservoir, its proper
frame should be no less than 3/8", and stances in which changes of tempera- conditioning is critical, and that
wider dimensions will help. The ture will cause the relative humidity to condition must be checked before it is
allowance between the edges of the move into a dangerous range. When a sealed in a package.
glass and the sides of the rabbet should window mat package for a work of art When the package for matted works
be roughly 1/8" at each edge and 1/4" on paper is sealed, the only air inside is begun, the mat package is laid on a
when considered together. If a frame will be that which is between the sheet of plastic/aluminum laminate
which has these dimensions cannot be fibers of both the board and the art, which is roughly 1" larger than the
found, it may be possible to use deco- and that which is in the opening of mat in every dimension. The glazing,
rative wooden fillet material to extend the window. The mass of cellulose in to which the hot melt glue has been
the lip or rabbet width of a frame the mat and the art will readily condi- applied, is cleaned and fitted onto the
which is available. tion that small quantity of air. As the front of the mat package. When all
There are two basic designs for temperature of the package drops and dust has been eliminated, the laminate
highly sealed packages, one for matted the air can hold less moisture, the can be tacked to the hot melt. This is
works on paper and one for paintings. cellulose will absorb that moisture. done by puffing it up and over the
10 PFM _ April Preservation Supplement 2002
glue and applying enough heat to fuse
it to the glue. At this point, the line of
glue will not have been flattened.
The heating proceeds along each side
toward the corners. The bonding of
the laminate to the corners is the most
important part of the sealing process,
since it is here that leaks are most
likely to occur. The laminate which has
been bonded to contiguous edges will
form a group of gathers at the corner.
This should be puffed together and
pulled toward one of the sides so that
heat can be delivered to its base [Figure
5]. This material should then be pulled
over toward the other adjacent side
and heat applied to its base on that
side. Finally, the material can be puffed
over toward a line which bisects the
angle which the corner forms and heat
can be delivered to the center of the
base of this gathered portion of lami-
nate. It can then be flattened [Figure
6]. The purpose of this elaborate
heating of the corner of the package is
insuring that this folded part of the
package does not have any remaining
gaps.
When the corners have been treated,
heat should be carefully applied to the
edges so that the hot melt under the
laminate is flattened and a firm bond
is established all around the package.
One sign that the seal is good in a
particular area is the oozing of the hot
melt from under the edge of the lami-
nate toward the center of the acrylic
glazing. When the bonding is complete
and the hot melt is cool, the laminate
can be trimmed using the same tech-
nique one would use to trim the paper
on the back of a frame. The finished
edge should look like Figure 7 in cross
section. This sort of sealing should be
practiced, and the practice packages
should have a compressible material in
them so that they can be squeezed to
test whether the seal has been achieved.
A properly sealed package will not
collapse when squeezed and when
more than one has been made during
practice, production can begin.
This package can be made water-
proof and may be useful if an item is
to be hung in a public place where it
April Preservation Supplement 2002_ PFM 11
may encounter water from a sprinkler the strips at the corners should be along the length of this intersection.
system. Since the acrylic glazing will drawn up so that their matte polyeth- This will create a flap which should be
permit a minute amount of water ylene sides face each other and are heated on both sides to ensure that it is
vapor to pass through it, such a aligned [Figure 11]. fully bonded [Figure 12]. The joined
package can not be left in high The sides are joined to each other edges of the material at the corners
humidity for indefinite periods. Glass with heat beginning at the overlap of should be bonded to the hot melt glue
can serve as an effective vapor barrier the edge of the glass and proceeding on the front of the glass with special
care to guard against the possibility of
remaining gaps. When the bonding of
Figure 8 Figure 9
the laminate to the front of the glazing
is complete and the corners have been
completed, heat should be applied to
the laminate where it passes over the
sides of the glass. The hot melt will
likely have extended slightly over the
edges of the glass, and this step will
bond the laminate more thoroughly
and will produce an edge which can be
and can be used to make packages completed more easily. When this
which will maintain their proper application of heat has been finished,
initial conditioning, but a more the front edge of the laminate may
complicated package and laminated show a ridge at its front outside edge
glass must be used. which will be a sign of good adhesion
This type of package uses two sepa- Figure 10 [Figure 13].
rate strips of plastic/aluminum lami- The glass can now be turned over
nate for each edge of the glass. One and narrower strips of the laminate can
strip will extend from the front edge be prepared. These should be cut in
Figure 11
of the glass, across the depth of the lengths equal to the dimensions of the
rabbet, and on to the back of the edges of the glass. A strip of board,
frame, where it will form a bonding equal in thickness to the package,
surface [Figure 8]. The other strip will should be cut so that it can be used as
be narrower and will go from the a bonding support. The narrow strips
inside edge of the glass and extend up can now be heat bonded to the hot
the depth of the rabbet, but no further melt on the inside of the glass and to
[Figure 9]. The wider strip is heat the inside of the wider strips [Figure
bonded onto the hot melt glue layer 14]. There will now be a nylon surface
which has been applied to the front which lines the inside of the package
side of the glazing along each edge. in all but the four corner areas. The
These strips should overlap their Figure 12a package will look like Figure 15 in
neighbors at the corners [Figure 10]. cross-section.
Their bonding is done in the same The remaining polyethylene surfaces
manner as was done with the acrylic can be joined to their neighbors with
sheet, with the strips first tacked in heat if the package is stood on edge
place and then pressed down onto a and heat is applied to the outside of
flattened glue mass with more heat. A each corner [Figure 16]. This will
problem which may be encountered create a package which has tough walls
here is that the capacity which glass
has for retaining heat will make the Figure 14
laminate film easy to dislodge for a
longer time than is the case with
acrylic sheet. Thus, when the second Figure 12b
application of heat is provided, care
must be taken that the tacking iron
Figure 13
does not twist or otherwise dislodge
the film. The overlapping portion of
12 PFM _ April Preservation Supplement 2002
and will fit into the frame. The corner indicative of a complete bond. More have folds in it. These areas should be
flaps should be wrapped around the time should be spent on the corners given enough heat so that the folds
corners so that it can be set in the where the material on the bottom will are flattened .
frame and the When the these seams are cool,
outer portion of Figure 15 their edges can be trimmed off inside
the wider strips the outside edge of the frame, just as
folded onto the if they were the edges of a sheet of
back of the frame backing paper. The painting can now
[Figure 17]. If the be secured in the package with
Figure 16
bonded strips at the corners do not lie padded mending plates which are
comfortably on the back of the frame, screwed into the back of the frame
they can be released from one another through the bonded portion of the
with heat which has been applied to package. The plates should be bent to
their outside surfaces so that the give them the proper shape and their
inside surfaces can be gently pulled ends, which will press on the
apart. Double-sided tape can be painting, should be given pads of
placed on the back of the frame so polyethylene foam held in place with
that it holds the laminate in place double-sided tape. When the plates
during the next steps. have been screwed in, a sheet of
This sort of package is useful with
anything which must be enclosed Figure 17
which does not have a window mat to
remove the edges of the work from
the heat needed to create the seal of
the package. The sealing done with
this package takes place on the back
of the frame and thus, away from its
contents. The spacer which will be
used to keep the work away from the
glazing can now be installed on the
edges of the glazing.
In the case of paintings, the spacer
can be made of strips of radiation
cross-linked polyethylene foam which
have been cut to the proper width and
secured with acrylic double-sided tape
to the glazing after it has been given a
final cleaning. The painting can now
be installed and shimmied into place
with more strips of the polyethylene
foam. If silica gel is used, openings
should be left in the shims around the
edges of the painting so that the air in
front of the painting can be affected
by the silica gel in back.
The package can now be closed
with a sheet of plastic/aluminum
laminate. This is cut so that it is larger
than the back of the frame and is laid
with the polyethylene side down over
the frame and its contents. It is
bonded with heat to the portion of
the strips which extend onto the back
of the frame. The heating should
produce the wrinkled appearance
April Preservation Supplement 2002_ PFM 13
polypropylene double-wall board can This may be done with the use of the glazing materials, ensuring that no
be cut so that it is slightly smaller scavenging materials, but there is no Newton rings will be produced by
than the back of the frame and can be way of knowing how these materials contact between the surface of the
secured to the frame with screws are functioning in the enclosure. A glazing materials. The viewer will see
through the bonded portion of the less sealed environment, which allows only the reflection on the surface of
laminate [Figure 18]. for off gassing beyond the frame, is the outer layer of glazing and their
This sort of package can also be probably wise. visual experience will not be marred
used with acrylic sheet glazing when by two sets of reflections.
paintings are being framed. If a Placing Potential Damaging Items in Materials such as rubber or wood
thicker type of sheet is used, it will a Sealed Frame may be enclosed in a sealed package
give greater resistance to the influx of When clients insist on housing mate- without ventilation to the exterior of
water vapor and will allow for more rials in a single frame which may the frame. Sealing a rubber item in a
frame will at least limit its exposure to
atmospheric oxygen and will shield
metals, especially silver, from the
sulfur that the rubber will emit. The
acids and peroxides that wooden
items emit will affect the wood itself,
but should not lead to its physical
breakdown if the wood is sealed.
Figure 18 Figure 19 The sealed package for these sorts
of items should include a support
ready adhesion of the laminate to the
Figure 20
edges of the sheet. Whether glass or
acrylic sheet is used, the double thick
walls of this package give it a greater
resistance to punctures, therefore it
will endure more handling than the
package designed for matted works
and will hold a heavier load.
The backing board must be behind affect one another chemically, the made of conservation-quality board
both types of packages to reduce the accommodations the framer should with margins large enough so that
possibility of punctures. An RH make for these materials should be heat can be applied to the edges (in
monitor can be included in either tailored to suit the gases each item order to bond the sealing laminate to
type of package. This can be done if emits. Woods and some plastics give the glazing) without any heat reaching
a cobalt salt card is cut so that a off acids and peroxides, other plastics the item itself. The inclusion of scav-
narrow strip of it can be secured give off chlorine, rubber gives off enging materials in the support mat
inside the package. It should be sulfur, and oxidizing metals can should benefit the enclosed item.
placed in an unobtrusive site under contaminate other items that are in These scavengers can include calcium
the lip of the frame so that it can contact with them. Each of these carbonate or zeolite found in
only be seen if special care is taken materials must be isolated from other matboard, copper-impregnated poly-
and will not be visible to the casual items in the frame, but some of them ethylene, silver cloth, or paper
viewer [Figure 19]. may even need to be ventilated to the impregnated with active charcoal.
The need for proper conditioning outside of the frame to slow their self- The glass that forms the front of
of the material inside the package destructive potential. the enclosure can be given a bead of
cannot be overstated. It is also unwise Glass and coated metals are the electrical grade, hot melt adhesive so
to seal in materials which may have essential constituents of isolation in that the plastic/metal laminate film
self-destructive potential. Obviously, framing. When an isolation package is can be bonded to its front edge with
such materials would not be included made with glass and metal/plastic heat. Since the package will be held
in the housing around the art, but laminate, it can be secured in the shut with the bonded laminate, the
when the art itself is made of such frame behind a sheet of acrylic item can be set in a sink formed to
materials, especially those which glazing. The acrylic will protect the the item’s contours and held away
produce acids which can build up glass from breakage. The matting from the glazing by a window mat,
over time, some provision for the needed to cover the edges of the without any further closure necessary.
uptake of the acid should be made. package will separate the surfaces of In cross-section, one such package
14 PFM _ April Preservation Supplement 2002
could look like Figure 20. Special Glazing Considerations
Early plastics are a more difficult Most frames can be successfully fit
challenge. Cellulose modified by with either glass or acrylic sheet;
acetic, nitric, or other acids will sealed frames have special considera-
produce those same acids over time. tions. Acrylic has the advantage of
These materials have shown a being virtually shatterproof in a frame
pronounced tendency to self- and can be found in a wide variety of
destruct, and enclosure in a sealed thickness and sizes, with or without
package may aggravate their condi- an ultraviolet absorber. Glass has
tion as the acids accumulate and more modest cost, low static poten-
cause further breakdown of the tial, and can act as a vapor barrier,
cellulose. These materials are which makes it valuable for the
difficult to maintain in the dark creation of sealed packages. Acrylic is
and their inclusion in a frame must hygroscopic and can transmit water
be discouraged. vapor. It can warp if the two sides of
If they have to be included, they the sheet are exposed to differing
should be isolated from anything else levels of relative humidity.
in the frame and provisions should For anti-reflectivity and stability in
be made so that their gaseous by- sealed packages that are expected to
products can safely escape from the resist climate change, glass is the only
frame. When such items are isolated option, with its heat resistance and
in the frame, the package in which
Figure 21
they are enclosed should be made so vapor barrier potential. The critical
that any off gassing can only escape problem with glass is its fragility.
out the back of the frame. Lamination of two lites of glass
Here, the package should be faced with a flexible core material is the
with glass, have sides of metal/plastic obvious answer. The fact that most
laminate, and a back of conserva- thin, flat glass is strengthened with
tion-quality matboard and acid-free iron creates an aesthetic problem,
corrugated board. The backing board since the presence of iron in the glass
should be open to the air behind the imparts a green tint, and when this
frame. This may entail its being inset tint is multiplied through lamination,
in the larger backing board which the resulting color seriously affects its
supports the entire contents of the color rendering. Glass with low iron
frame. This package could look like content is beginning to become avail-
Figure 21. able to framers, with and without
The vast majority of materials anti-reflective coating. Low iron, anti-
presented to framers for framing are reflective, laminated glass has enjoyed
chemically stable and the only risk widespread usage in museums, but its
they pose is their potential sensitivity high cost and limited availability has
to light. When sports and other kept it from use in general framing.
memorabilia are proposed for inclu- The combination of no reflections,
sion in a shadow box, the possibility utter clarity, ultraviolet control, effec-
of substitution of a facsimile and tive vapor barrier potential, and
storage of the original material in a shatter resistance adds up to the ulti-
box should be the first option. mate in glazing products—virtual
April Preservation Supplement 2002_ PFM 15
invisibility with profound protection. on the sheet at the appropriate point two sets of reflections will not be
However, its cost will likely keep it in on both. The scores must be run, or evident enough to cause an aesthetic
the highest end of the framing cracked open, with a combination of distraction.
market. If the anti-reflective coatings tapping along them with a screwdriver This type of package will give some
are left out, the resulting product and very gentle pressure. The tapping protection from breakage, but a
would have all but one of those attrib- and pressure will open the score that strong blow to the surface of the outer
utes and should be available at a is on the lite of glass that is on the layer of glazing or severe corner-to-
much lower cost. bottom. When both scores have been corner twisting could break the inner
Such low iron, UV absorbing, lami- run and this fact has been confirmed layer of glass. This would leave the art
nated glass could be made without the through careful examination with a exposed to broken glass edges.
production demands (and therefore raking light, the sheet can be gently Reversing the layers of glass and
high cost) of AR glass. This glass flexed along the open scores to expose acrylic can address this problem. This
could be used in framing valuable the plastic laminate for cutting. Once strategy, which was suggested by
works, ensuring their safety and the the excess has been removed, the Virginia Ritchie, a museum preserva-
clear rendering of their colors. It edges of the glass can be dulled with tion framer, will entail the creation of
could be use in the creation of highly an edge seamer. a thicker package, which must be
sealed packages that would not lose When a laminated glass product is strengthened to accommodate the
their initial conditioning over time. not available, the simplest approach acrylic sheet within, but it will elimi-
The only impediments to introduc- would be to install a sheet of acrylic nate any possibility of glass shards
tion of such a product are the need in front of a sealed package that has cutting the art.
for more two-millimeter, low iron been made with glass. If the two This package can be made using the
glass and the skill needed for sizing glazing sheets are spaced apart with same aluminum/plastic laminate sheet
laminated glass. strips of matboard, they should not and electrical-grade hot melt adhesive
Trimming lites of laminated glass to touch and Newton rings should be as the packages described earlier.
specific sizes entails scores being made prevented. Also, the fact that there are The hot melt that is used to seal the
16 PFM _ April Preservation Supplement 2002
package can also be used to hold the placed so that its polyethylene side is achieved, the package can be carefully
acrylic sheet and the glass apart. down and its nylon side is up. It moved to the edge of the work surface
While the bead of hot melt is being should be adjusted so that it extends and stationed at the proper distance
extruded onto the edges of the lite of out from under the mat just far so that the portion of the sheet not
glass, a similar bead can be set on the enough that it will cover the side of covered by the 1" strip can be folded
edges of the acrylic. This down over the edge of the table. This
latter layer of glue should be will keep it from becoming stuck to
thick enough to hold the the tacking iron when heat is used to
glazing layers far enough attach the strip to the laminate sheet
apart to avoid Newton rings. [Figure 22].
The fact that there will be The tacking iron is now used to
an extra layer of glazing, and Figure 22 bond the strips in place. When that
the spacing needed to has been completed, the laminate is
accommodate it, means that pulled onto the hot melt glue on the
the package will be thicker front edges of the glass and bonded
than normal. In a normal with heat, as usual. The finished
package for a matted work, Figure 23 package will look like the cross-
the laminate sheet should be section seen in Figure 23.
at least 1" larger than the glazing on the package when it is pulled around The added thickness of this type of
each side. Here the laminate should to the front of the glazing, but it will package will make the closure of the
be an 1 1/2" larger than the glazing not extend around to the front of the front corners a bit more difficult. The
on all sides. glazing. laminate will seal best if it is pulled
The other difference between this When this position has been onto the front of the glazing in a
package and an ordinary one is the
inclusion of the sheet of acrylic inside
the package. If the walls of the
package were not reinforced, the
acrylic sheet inside the package might
shift during handling and rupture the
laminate that surrounds it. The lami-
nate comprises four layers, (nylon on
the outside, polyethylene, aluminum,
and polyethylene), and if its integrity
is challenged on the inner polyeth-
ylene side, it will begin to give way
before the tougher nylon layer is
reached.
The best way to prevent any threat
to the sides of the package from the
glazing involves reinforcing the sides
with another layer of laminate. Strips
of laminate roughly 1" wide, and as
long as the vertical and horizontal
dimensions of the glazing, should be
prepared. The cleaned glazing combi-
nation can be fitted to the front of the
mat package.
The laminate sheet can now be laid
on the work surface with its polyeth-
ylene side up and the mat/glazing
package can be laid in the center of
the sheet. A 1" strip of appropriate
length can be slipped between the
back of the mat and the front of the
sheet of laminate. The strip should be
April Preservation Supplement 2002_ PFM 17
number of small folds, and the successful corners and well-sealed a package that is both safe and
thicker side of this package will tend packages. attractive.
to reinforce the tendency of the lami- The two layers of glazing will Using two layers of glazing will
nate to fold only along the corner reduce the transmission of light and add to the cost of the frame and will
edge. A bit of practice at manipu- low iron or water white glass is very require the use of a frame with a
lating the laminate into multiple folds helpful here. It can be combined deeper rabbet. However, the labor
will lead to the production of fully with UV-filtering acrylic to create required for the creation of a highly
sealed package already increases its
price and the preservation benefits
that this technology confers on high
value items should be worth the extra
cost.
A similarly sealed package can be
made for enclosing paintings and
objects as well. However, its design
will differ from the matted package
since it cannot be sealed with heat
around the front margins of the
glazing due to the proximity to the
work inside the package.
A package that has two layers of
glazing will look best if the glazing
materials are as clear as possible.
Fortunately, low iron or water white
glass with anti-reflective coatings can
be had from more than one vendor
and will enhance the appearance of
the work within. However, the AR
glass will not cancel the reflections on
the acrylic and some of its efficacy
may be lost when it is combined with
the acrylic. If an ultraviolet absorber
is needed, it can be provided through
the inclusion of an absorber in the
acrylic or in a coating on the glass.
Creating the package begins with
the glass being thoroughly cleaned
and beads of electrical grade hot melt
adhesive being extruded onto the
outer edges of both sides of the glass.
Strips of plastic/aluminum laminate
can be used. Whichever material is
chosen, it can then be cut so that they
are 3" to 4" wide and longer than
each side of the glass by twice the
width of the strips.
The polyethylene side of these
strips can be bonded to the hot melt
with a tacking iron so that the strips
overlap onto the front of the glass by
1/8" and will overlap the neighboring
strips at each end. When the hot melt
is flattened and the surface of the
laminate is finely wrinkled, the bond
should be complete.
18 PFM _ April Preservation Supplement 2002
The overlapping ends of the strips The bulk of the laminate that package should be sized so that it is
can now be folded up above the front surrounds the edges of the glass will 1/16" smaller than the glass. That will
of the glass so that their polyethylene probably require that the frame be allow it to fit inside the package.
sides meet along a mitered line rabbeted out to accommodate it. The Its edges should be rounded with an
extending out from the corner of glass should not be cut smaller than edge seamer or a plastic file so that
the glass for heat bonding there. normal to fit the frame, since that they will not puncture the walls of the
When the corners have been would make the package too tight for package. A bead of hot melt can be
bonded, the glass can be turned over its painting. extruded onto the edges of one side of
and four more strips of laminate, 2" If, instead, the rabbet dimensions of the acrylic to form a spacer that will
wide and equal in length to the sides frame are enlarged, the frame will keep its surface from touching the
of the glass, can be heat bonded to have a larger lip or rabbet width and surface of the glass.
the inside of the outer strips. The should cover the laminate at the edge The cleaned acrylic can be fitted
inner strips should be positioned so of the glass, while giving adequate inside the cleaned glass of the
that they lap onto the bead of hot room for the painting [Figure 24]. package, without bonding to the glass
melt on the inner surface of the glass The acrylic that will fit inside the or package. This will allow for the two
and they should be bonded onto the layers to be separated when a piece of
outer strips to a width, equal to the Figure 24 framing detritus is spied in between
width of the tacking iron. them. A spacer of conservation-
When this is complete for all four quality board or painted balsa can be
sides, the package can be stood on tacked onto the surface of the acrylic
edge and heat applied to the outside with hot melt to keep the painting
of the outer strips at each corner. This away from its surface, before the
will form a joint that is perpendicular acrylic is installed in the package.
to the plane of the glass. The package Finally, the painting is fitted into
is now ready for installation in the the package as it sits in the frame, and
frame. a sheet of laminate is heat bonded to
April Preservation Supplement 2002_ PFM 19
the outer edges of the package, where
they overlap the back side of the Chemical Interactions Inside the Frame
frame. The painting is secured with Once frame sealing is considered, a brief overview of chemical issues in framing can be useful.
pressure applied through the back The choices for glazing between glass and polymer sheeting does not have too many chemical consequences.
sheet of laminate by brass mending Both types of material have long histories of intimate proximity to sensitive objects with little appreciable effect.
plates. These plates are screwed to the When works are in contact with glass, there may be some possibility of chemical change on the part of the
back of the frame through the glass. The white material which can be seen as a ghost image on the glass of some old frames has proven in some
bonded part of the package and a cases to be sodium chloride (table salt). This may result from sodium, which is a very common component of
sheet of polypropylene double-wall is glass, leaching out of the glass and combining with chlorine contributed by something in the environment.
screwed to the frame through that This is a situation which can be avoided by properly spacing the work in the frame away from the glass. Even if
same bonded outer portion of the salt were transferred to the surface of the paper, it may not have consequences which are too devestating. Salt has
package to protect the package and been used in some watercolor and photographic techniques without obvious degradation of the paper.
the painting from punctures. When ultraviolet absorbers are included in glazing materials, they should not pose a chemical danger. In the
This sort of enclosure, if properly case of glasses, they will be deposited on the surface in a matrix which will contain them, or they will be in the
conditioned and sealed, will protect laminate between two lites of glass. In the case of acrylic sheet, they will be in the body of the sheet and should
its contents for as long as the seal is not be expected to migrate out. The presence of the ultraviolet light absorber will have the effect of reducing the
maintained. The longevity of such chemical reactions in the art as it removes the most energetic wavelengths and the chemical changes which they
protection is even more important in would initiate.
a private setting than it is a museum, The role that a frame might play in the chemical interactions within a frame package will depend on its material
where works are routinely unframed and design. A metal frame is not likely to be made of an alloy or metal which would oxidize readily. (This is
as part of their maintenance. because the oxidation would be aesthetically disfiguring.) Metal coverings used on frames are also likely to be
Our increasing experience with either non-tarnishing (like gold) or sealed.
such enclosures will inform our Thus, framers are likely to encounter anodized aluminum, karat gold, or brass, aluminum, or silver leaf which
future designs, increasing their dura- has been coated. Each of these materials should have little chemical potential for interacting with the contents of
bility and powers of sequestration, the frame. Indeed, metal coverings on wooden frames can reduce the potential which the wood has to affect the
but preservation must always be seen framed material chemically.
as a continuing enterprise, where Since all wood has lignin binding it together, it has the potential to cause discoloring oxidation in materials to
items not left in even the most care- which it is proximate. If the art is separated by a barrier layer lining the rabbet or by a wide enough expanse of
fully designed enclosures forever, but mat board, (1"), it should be safe from this degradation.
are monitored regularly and carefully The recent advent of frames made of synthetic polymers raises the issue of their potential off gassing. The
to ensure their safe maintenance. ■ brevity of our experience with these materials means that we lack anecdotal evidence for their behavior over time.
It may be that some of them will not contribute chemically to the materials which they enclose, but until that has
been shown, it is wise to treat they as if they were as reactive as wood and provide for a barrier between them
and the art or a distinct buffering margin of mat board.
Hugh Phibbs has worked in preservation Matting materials can provide the most chemically beneficial component of the entire frame. They can support
framing for more than 25 years; in a the art and insulate it from physical damage without causing chemical change.
commercial shop and in The cellulose which is the primary constituent of mat board is chemically stable, especially in its non-branching,
the Conservation Division or alpha, type. A layer of pure cellulose is the best choice for a material which will come in contact with a work of
of the National Gallery
art on paper. If pigment is added throughout the board, it is unlikely to pose a chemical problem. The pigment
of Art. He was a
compiler of the should be kept below the level of density at which it might rub or crock off onto the art to avoid physical problems.
Matting/Framing section Since the fibers which comprise the board will not receive printing, the need for harmful sizings, such as are
of the Book and Paper found in some papers, is not present. Any finishing or sizing of the board is likely to be benign, since manufacturers
Group of the American frequently use such exacting standards as the Photo Activity Test for assaying their products. When calcium
Institute for Conservation’s Treatment
carbonate or molecular sieves are added to the board, they provide more protection for the board itself and the
Outline. He is a Professional Associate of
the American Institute for Conservation and
material it houses.
a former board member of the Washington The material which comprises the backing board is usually selected for its ability to provide rigidity and resist-
Conservation Guild. He has written “Preser- ance to punctures without significant weight or expense. The best papers used in these boards are free of lignin and
vation Practices,” a monthly column on harmful additives. This will extend their useful life and eliminate any possible chemical contribution to the frame
preservation and numerous preservation package from that source. When backing boards contain plastics, they are likely to be polypropylene or poly-
supplements for Picture Framing Magazine,
styrene. These can be weakened by oxidation and ultraviolet. Since they will not be exposed to light, the latter
as well as an article on preservation for
Decor magazine. He has taught workshops problem is not likely to result and, therefore, off gassing from that source is unlikely. Indeed, any off gassing which
for the conservation programs at Winterthur, occurs is likely to be minimal.
NYU, and SUNY, Buffalo. He has also Since the backing board should be isolated from the art by at least one sheet of conservation-quality board, its
taught classes for the American Institution for potential for reacting with the art is limited. The role it plays in sequestering the art from chemical change from
Conservation, The Smithsonian Resident
without is more relevant. Here, the polymers in the boards can slow the passage of atmospheric gasses into the
Associate’s Program, the PPFA, PFM Semi-
nars and The National Conference.
package. ■
20 PFM _ April Preservation Supplement 2002